Copper alloys of improved characteristics



i atented Nov. 15, 1938 COPPER ALLoYs F IMPROVED CHARAC- mms'rrcs FranzR. Hcnsel and Earl I. Larsen, Indianapolis,

Ind., assignors to P. R. Mallory & Co., Inc., Indianapolis, Ind., acorporation of Delaware I No Drawing. Application July 13, 1938,

Serial No. 218,970

3 Claims.

This invention relates to alloys, and more particularly to copper alloysof improved characteristics.

An object of the invention is to produce an improved copper base alloy.

Other objects of the invention will be apparent from the followingdescription, taken in connection with the appended claims.

The present inventioncomprises a combinalO tion of elements, methods ofmanufacture and the product thereof, brought out and exemplified in thedisclosure hereinafter set forth, the scope of the invention beingindicated in the appended claims.

While a preferred embodiment of the invention is described herein, it iscontemplated that considerable variation may be made in the method ofprocedure and a combination of elements without departing from thespirit of the invention. .Prior work on copper-silver-tin alloys hasshown that these materials possess a number of desirable properties,particularly if tin and silver are present only in small percentages.Such alloys combine with a high annealing point excellent cold workingproperties. Preferred compositions for this type of alloy contain up to1% tin and up to silver. By going to higher silver contents, such as 2silver, certain aging phenomena can be obtained in these alloys; 0 suchaging, however, is manifested more in improvements in electricalconductivity than in improvements in hardness. Due to the fact that thecopper-silver system is inherently an age hardening system, theannealing point of copper- 5 silver-tin alloys, which have been severelycold Worked is fairly high. Silver furthermore has the outstandingadvantage that it will not decrease the electrical conductivitymaterially when alloyed with copper. This is due to the limited 40 solidsolubility of silver in copper at temperatures 'below 200 degrees C. Wehave found that at 600 degrees C. approximately 2 silver can be held insolid solution, while at 200 degrees C., only .3% silver is held insolid solution and at room temperature, this solubility is still less.

Alloys consisting of copper, tin and silver, have, in addition to thehigh annealing point andcold workability, also excellent corrosionresistance and particularly resistance to sea water corrosion. If theelements tin and silver are used in higher proportions, castings can bemade in which tin is used to increase both the strength and yield point.It is impossible, however, to exceed the solubility of tin in copper,otherwise a constituent is formed which is generally known as the deltaconstituent, and forms hard spots which interfere with the machiningproperties. In order to overcome such difficulties, the presentinvention describes the addition of beryllium to an alloy of copper,silver and tin, and therewith combining the effects of the agehardening. characteristics of the copper-beryllium system with thedesirable properties of the copper-silver-tin alloys.

The alloy of the present invention may preferably contain the essentialingredients in the following proportidns:

Per cent Beryllium .03-3 Silver .05-4 Tin .05-12 Copper Balance.

Within these composition ranges, there area number of specific alloyswhich have been found to be of particular importance. Four of the Thealloys can be made according to standard alloying methods, such asmelting the copper, adding the desired amounts of tin and silver, andafterwards adding the correct amount of beryllium, either in the form ofa copper-beryllium .master alloy, or any other form. The material can becast either in a chill mold or in sand molds, at the correcttemperature, and the alloy can be used in the as cast condition, or canbe further worked by means of rolling, extruding, drawing, forging orsimilar methods.

'After the alloy has been prepared according to standard alloyingmethods, the heat treatment may be carried out as follows:

The alloy in the form of a billet or a sand casting or any desired form,is raised in temperature to between 700 degrees C., and its meltingpoint. The alloy is then quenched from this temperature and subsequentlyaged at temperatures below 600 degrees C. This heat treatment results inconsiderable improvements in the physical properties of the alloy.

If the alloy, after casting, is rolled, it has been found desirable toquench the alloy before rolling and aging same after rolling. The coldworking operation between quenching and aging increases the hardnessvery considerably. It was found that in the new alloys disclosed, theaddition of tin allows one to greatly reduce the beryllium content, inorder to .obtain the same hardness. It is possible, for instance, totake an alloy of approximately 8% tin, .5% silver, .'15%

beryllium, balance copper, and obtain -a Brinell hardness of 350 byquenching the material, before rolling from approximately 800 degrees C.and subsequently aging same at between 250 and 800 degrees C. The amountof rolling between quenching and aging may vary from 25 to 75% coldreduction, the amount of cold reduction determining partly the finalhardness which can .be reached. The alloy is particularly suitable forapplications in which high elastic properties and high annealingtemperatures are required. At the same time, the alloys show a goodelectrical and thermal conductivity. The alloys have found furtherextensive use in applications where the material is used for electricalcontacting purposes, such as contactor contacts. where surface oxidationproduces high resistance films on ordinary copper alloys.

The alloys have further found considerable use for wear resistancepurposes and applications such as special welding electrodes andresistance welding dies in general.

The alloys are furthermore very suitable for springs, particularlysprings which have to carry current, or which have to withstand certaintemperature rises, without losing their elastic properties.

The materials are also suitable forspecial applications where springs ofintricate desiln must be formed in the hardened condition, that is,after quenching and where high hardness can be reached after a suitableage hardening treatment. 5

The alloys are particularly suitable for any parts in electricalmachinery, where the combination of silver, beryllium and tin producesthe desirable characteristics required for such applications. 10

While the present invention as to its objects and advantages has beendescribed herein, as carried out in specific embodiments thereof, it isnot desired to be limited thereby, but it is intended to cover theinvention broadly, within the 15 spirit and scope of the appendedclaims.

What is claimed is:

1. An age hardened alloy composed of:

' Per cent Beryllium .oa- 3 Silver .05- 4 Tin .05-12 Balancesubstantially all copper characterized by high hardness and electricalconductivity, and further characterized by the 25 fact that its hardnessand conductivity are not permanently adversely afiected by elevatedtemperatures.

' 2, An alloy composed of:

FRANZ R. HENSEL. EARL I. LARSEN.

